| The endosperm storage proteins of bread wheat are the major determinants of baking quality of flour. Biochemical and genetic studies have revealed that the wheat glutenin, particularly, HMW-GS(High Molecular Weight Glutenin Subunit), are the major limiting factor for breeding potential of various varieties. Among the various HMW-GS, the 5+10 encoded at the Glu-Dl locus contributes the most to the high baking quality of wheat flour. To our knowledge, there have no reports for the presence of the 5'+12 HMW-GS in hexaploid wheat. A novel wheat line having a new HMW-GS 5'+12 was developed using inter-specific cross in this study. The molecular characterization of this new HMW-GS5'+12 was conducted, and the quality of flour from this novel wheat line was determined. In addition, Wheat lines chosen for provincial and national field tests are some of the best ones newly bred by various institutes, and are important germplasm for breeding and excellent candidates to be promoted for large-scale production. It is, thus, vital to study their genetic characteristics related to grain quality. This study characterized the genetic composition and diversity of HMW-GS, and their impact on grain quality in all wheat from the tests in Sichuan province, national initial and final tests, using techniques such as SDS-PAGE, SDS-sedimentation test, identification of 1RS.1BL translocation. Through these analyses, deficiencies in grain quality related to HMW-GS were identified in various wheat varieties,particularly in those grown in Sichuan province. Strategies for quality improvement in various varieties were proposed. Based on the results from this study, the following conclusions were drawn.1. A novel wheat line possessing new high-molecular-weight glutenin subunits(HMW-GS) 5'+12 was developed by using interspecific cross (T.durum Desf XT.aestivum L.) in this study. The SDS-PAGE analyses demonstrated that this new germplasm possessing HMW-GS 5 and 12 at Glu-Dl loci. PCR based assays were also used to identify the Glu-Dl locus, there are small difference of DNA sequences was found between the Dx5' gene in HMW-GS 5'+12 and the Dx5 gene in HMW-GS 5+10 by using defferent specific PCR primers to Dx5 gene, indicating the Dx5' was a new gene at Glu-Dl locus and the HMW-GS5'+12 is a new combination which have never been report. The inheritance of HMW glutenin subunits 5'+12 in F1 is consistent with the co-dominant type, and the segregation regularity in F2 differing from the parent, subunits 5+12, 2+12 and 2+5+12 have the same frequency in F2 when the cross between subunits 5'+12 and 2+12, however subunits 5+12 have higher frequency than 5+10 and 5+10+12 in F2 when the cross between subunits 5'+12 and 5+10.The relative content of mono-subunits in total HMW glutenin subunit was analyzed by using computer, it was found that the relative content of y-type subunit 12 in subunit combination 5'+12 was higher than y-type subunit 10 in subunit combination 5+10. There are various studies showing that HMW glutenin subunits 5+10 is associated with the best bread-making quality. However, Lines possessing HMW-GS 5'+12 subunits were superior in many quality parameters, sedimentation value, wet gluten content, development time and stability time of farinograph as compared to their siblines containing HMW-GS 5+10, This indicate the HMW-GS 5'+12 can result in stronger gluten and improve the gluten quality. This novel line also has high yielding characters in multi-florets, and can be an extremely useful genetic resources for breeding wheat varieties with good grain quality.2. There are rich diversity of HMW-GS and their combinations in wheat varieties chosen from Sichuan provincial tests. The HMW-GS at Glu-Bl locus, 13+16,514+15 and 6+8, were among the novel ones that were introduced into varieties in Sichuan province in recent years. The occurrence frequency of the HMW-GS of 5+10 at Glu-Dl locus in these wheat varieties has exceeded that of the 2+12 HMW-GS, indicating that the superior 5+10 have been bred... |
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